1. Field of the Invention
The present invention relates to a composite thin-film magnetic head comprising a reproducing head and a recording head and to a method of manufacturing such a thin-film magnetic head.
2. Description of the Related Art
Performance improvements in thin-film magnetic heads have been sought as surface recording density of hard disk drives has increased. Such thin-film magnetic heads include composite thin-film magnetic heads that have been widely used. A composite head is made of a layered structure including a recording head having an induction-type magnetic transducer for writing and a reproducing head having a magnetoresistive (MR) element for reading.
It is required to increase the track density on a magnetic recording medium in order to increase recording density among the performance characteristics of a recording head. To achieve this, it is required to implement a recording head of a narrow track structure wherein a track width, that is, the width of top and bottom poles sandwiching the recording gap layer measured in the air bearing surface, is reduced down to microns or the submicron order. Semiconductor process techniques are utilized to implement such a structure.
Reference is now made to FIG. 16A to FIG. 19A and FIG. 16B to FIG. 19B to describe an example of a method of manufacturing a composite thin-film magnetic head as an example of a related-art method of manufacturing a thin-film magnetic head. FIG. 16A to FIG. 19A are cross sections each orthogonal to an air bearing surface of the head. FIG. 16B to FIG. 19B are cross sections of a pole portion of the head each parallel to the air bearing surface.
In the manufacturing method, as shown in FIG. 16A and FIG. 16B, an insulating layer 102 made of alumina (Al2O3), for example, and having a thickness of about 5 to 10 xcexcm is deposited on a substrate 101 made of aluminum oxide and titanium carbide (Al2O3xe2x80x94TiC), for example. On the insulating layer 102 a bottom shield layer 103 made of a magnetic material is formed for making a reproducing head.
Next, on the bottom shield layer 103, alumina, for example, is deposited to a thickness of 100 to 200 nm through sputtering to form a bottom shield gap film 104 as an insulating layer. On the bottom shield gap film 104 an MR element 105 for reproduction having a thickness of tens of nanometers is formed. Next, a pair of electrode layers 106 are formed on the bottom shield gap film 104. The electrode layers 106 are electrically connected to the MR element 105.
Next, a top shield gap film 107 is formed as an insulating layer on the bottom shield gap film 104 and the MR element 105. The MR element 105 is embedded in the shield gap films 104 and 107.
Next, on the top shield gap film 107, a top-shield-layer-cum-bottom-pole-layer (called a bottom pole layer in the following description) 108 having a thickness of about 3 xcexcm is formed. The bottom pole layer 108 is made of a magnetic material and used for both a reproducing head and a recording head.
Next, as shown in FIG. 17A and FIG. 17B, on the bottom pole layer 108, a recording gap layer 109 made of an insulating film such as an alumina film whose thickness is 0.2 xcexcm is formed. Next, a portion of the recording gap layer 109 is etched to form a contact hole 109a to make a magnetic path. On the recording gap layer 109 in the pole portion, a top pole tip 110 made of a magnetic material and having a thickness of 0.5 to 1.0 xcexcm is formed for the recording head. At the same time, a magnetic layer 119 made of a magnetic material is formed for making the magnetic path in the contact hole 109a for making the magnetic path.
Next, as shown in FIG. 18A and FIG. 18B, the recording gap layer 109 and the bottom pole layer 108 are etched through ion milling, using the top pole tip 110 as a mask. As shown in FIG. 18B, the structure is called a trim structure wherein the sidewalls of the top pole portion (the top pole tip 110), the recording gap layer 109, and a part of the bottom pole layer 108 are formed vertically in a self-aligned manner.
Next, an insulating layer 111 made of an alumina film, for example, and having a thickness of about 3 xcexcm is formed on the entire surface. The insulating layer 111 is then polished to the surfaces of the top pole tip 110 and the magnetic layer 119 and flattened.
Next, on the flattened insulating layer 111, a first layer 112 of a thin-film coil is made of copper (Cu), for example, for the induction-type recording head. Next, a photoresist layer 113 is formed into a specific shape on the insulating layer 111 and the first layer 112. Heat treatment is then performed at a specific temperature to flatten the surface of the photoresist layer 113. On the photoresist layer 113, a second layer 114 of the thin-film coil is then formed. Next, a photoresist layer 115 is formed into a specific shape on the photoresist layer 113 and the second layer 114. Heat treatment is then performed at a specific temperature to flatten the surface of the photoresist layer 115.
Next, as shown in FIG. 19A and FIG. 19B, a top pole layer 116 is formed for the recording head on the top pole tip 110, the photoresist layers 113 and 115, and the magnetic layer 119. The top pole layer 116 is made of a magnetic material such as Permalloy. Next, an overcoat layer 117 of alumina, for example, is formed to cover the top pole layer 116. Finally, lapping of the slider is performed to form the air bearing surface 118 of the thin-film magnetic head including the recording head and the reproducing head. The thin-film magnetic head is thus completed.
FIG. 20 is a top view of the thin-film magnetic head shown in FIG. 19A and FIG. 19B. The overcoat layer 117 and the other insulating layers and insulating films are omitted in FIG. 20.
In FIG. 19A, xe2x80x98THxe2x80x99 indicates the throat height and xe2x80x98MR-Hxe2x80x99 indicates the MR height. The throat height is the length (height) of the pole portions, that is, the portions of the two magnetic pole layers facing each other with the recording gap layer in between, the length between the air-bearing-surface-side end and the other end. The MR height is the length (height) between the air-bearing-surface-side end of the MR element and the other end. In FIG. 19B, xe2x80x98P2Wxe2x80x99 indicates the pole width, that is, the track width of the recording head (hereinafter called the recording track width). In addition to the factors such as the throat height and the MR height, the apex angle as indicated with xcex8 in FIG. 19A is one of the factors that determine the performance of a thin-film magnetic head. The apex is a hill-like raised portion of the coil covered with the photoresist layers 113 and 115. The apex angle is the angle formed between the top surface of the insulating layer 111 and the straight line drawn through the edges of the pole-side lateral walls of the apex.
As the reproducing output of the reproducing head increases, noise such as Barkhausen noise increases, and variations in output increase, with regard to the composite thin-film magnetic head wherein the bottom pole layer of the recording head also functions as the top shield layer of the reproducing head as shown in FIG. 19A and FIG. 19B, the composite head being capable of attaining surface recording density as high as 20 gigabits per square inches or 30 gigabits per square inches. A variation in output may be represented by COV (%), that is, a value obtained by dividing the standard deviation of the output by the mean value of the output, the standard deviation being obtained by measuring the output 100 consecutive times, and multiplying the result by 100. In this case, a variation in output is great if the COV is great.
One of the factors that cause an increase in noise and an increase in output variation of the reproducing head as mentioned above is residual magnetism and variations therein that are produced in the recording head capable of attaining high surface recording density, as the recording head performs recording.
It is an object of the invention to provide a thin-film magnetic head and a method of manufacturing the same for reducing noise and output variations in a reproducing head that result from the writing operation of a recording head.
A thin-film magnetic head of the invention comprises a medium facing surface that faces toward a recording medium, a reproducing head, and a recording head. The reproducing head includes: a magnetoresistive element; and a first shield layer and a second shield layer for shielding the magnetoresistive element, portions of the shield layers located on a side of the medium facing surface being opposed to each other with the magnetoresistive element in between. The recording head includes: a first magnetic layer and a second magnetic layer magnetically coupled to each other and including magnetic pole portions opposed to each other and placed in regions of the magnetic layers on a side of the medium facing surface, each of the magnetic layers including at least one layer; a gap layer provided between the pole portions of the first and second magnetic layers; and a thin-film coil at least a part of which is placed between the first and second magnetic layers, the at least part of the coil being insulated from the first and second magnetic layers. The second shield layer functions as the first magnetic layer, too. The thin-film magnetic head further comprises a nonmagnetic layer located in the second shield layer and between the magnetoresistive element and the pole portion of the second shield layer, the nonmagnetic layer having an area greater than an area of the magnetoresistive element.
A method of the invention is provided for manufacturing a thin-film magnetic head comprising a medium facing surface that faces toward a recording medium, a reproducing head, and a recording head. In the thin-film magnetic head the reproducing head includes: a magnetoresistive element; and a first shield layer and a second shield layer for shielding the magnetoresistive element, portions of the shield layers located on a side of the medium facing surface being opposed to each other with the magnetoresistive element in between. The recording head includes: a first magnetic layer and a second magnetic layer magnetically coupled to each other and including magnetic pole portions opposed to each other and placed in regions of the magnetic layers on a side of the medium facing surface, each of the magnetic layers including at least one layer; a gap layer provided between the pole portions of the first and second magnetic layers; and a thin-film coil at least a part of which is placed between the first and second magnetic layers, the at least part of the coil being insulated from the first and second magnetic layers. The second shield layer functions as the first magnetic layer, too.
The method of the invention includes the steps of forming the reproducing head; forming the recording head; and forming a nonmagnetic layer in the second shield layer and between the magnetoresistive element and the pole portion of the second shield layer, the nonmagnetic layer having an area greater than an area of the magnetoresistive element.
According to the thin-film magnetic head or the method of manufacturing the same of the invention, the nonmagnetic layer is provided in the second shield layer and between the magnetoresistive element and the pole portion of the second shield layer. The nonmagnetic layer reduces the effect of residual magnetism produced in the recording head on the magnetoresistive element.
According to the thin-film magnetic head or the method of manufacturing the same of the invention, the second shield layer may include: a first layer located to face toward the at least part of the coil; and a second layer including one of the pole portions and connected to a surface of the first layer that faces toward the gap layer.
According to the thin-film magnetic head or the method of manufacturing the same of the invention, the nonmagnetic layer may be located between the first layer and the second layer.
According to the thin-film magnetic head or the method of manufacturing the same of the invention, the second layer may include a portion for defining a throat height. In this case, the portion for defining the throat height may have a length between an end thereof located in the medium facing surface and the other end, the length being greater than a length of the nonmagnetic layer between an end thereof located in the medium facing surface and the other end.
According to the thin-film magnetic head or the method of manufacturing the same of the invention, the thin-film coil may include a portion located on a side of the second layer. In this case, an insulating layer may be further provided. This insulating layer covers the at least part of the thin-film coil located on the side of the second layer, wherein a surface of the insulating layer facing toward the gap layer is flattened together with a surface of the second layer facing toward the gap layer.
According to the thin-film magnetic head or the method of manufacturing the same of the invention, the second magnetic layer may be made up of one layer.
According to the thin-film magnetic head or the method of manufacturing the same of the invention, the second magnetic layer may include: a pole portion layer including one of the pole portions that defines a track width; and a yoke portion layer forming a yoke portion and connected to the pole portion layer.
According to the thin-film magnetic head or the method of manufacturing the same of the invention, the yoke portion layer may have an end face that faces toward the medium facing surface, the end face being located at a distance from the medium facing surface.
According to the thin-film magnetic head or the method of manufacturing the same of the invention, the pole portion layer may have a length between an end thereof located in the medium facing surface and the other end, the length being greater than a length of the magnetoresistive element between an end thereof located in the medium facing surface and the other end.
According to the thin-film magnetic head or the method of manufacturing the same of the invention, the thin-film coil may include a portion located on a side of the pole portion layer. In this case, an insulating layer may be further provided. This insulating layer covers the portion of the coil located on the side of the pole portion layer and has a surface facing toward the yoke portion layer, the surface being flattened together with a surface of the pole portion layer facing toward the yoke portion layer.
Other and further objects, features and advantages of the invention will appear more fully from the following description.